1. Field of the Invention
The present invention relates to the field of bookbinding, and is specifically concerned with bookbinding strips for binding together perforated sheets and the like, a method of binding perforated sheets with the bookbinding strips, and a book bound together with the bookbinding strips.
2. Description of the Prior Art
A variety of methods and bookbinding devices are known for holding a collection of pages or sheets together to form books, filings, price lists, catalogs, booklets, and the like.
For example, there are spiral devices and methods of bookbinding disclosed in Emmer U.S. Pat. Nos. 2,099,881 and 2,450,785, Mevi U.S. Pat. No. 2,116,078, and Friedman U.S. Pat. No. 4,374,627. Another example of the spiral device is the GBC (General Binding Corporation) plastic spiral comb. The spiral devices require large storage areas to store the different sizes (sometimes 16 different sizes) of combs, and this is a disadvantage.
Another bookbinding device is the loose-leaf binder, which uses spring-loaded semi-circular snap rings to hold a collection of pages together. An advantage of the loose-leaf binder is that the collection of pages held by the loose-leaf binder may be easily updated by opening the snap rings, removing the old page(s) from the opened snap rings, adding the updated page(s) to the opened snap rings, and closing the snap rings. Disadvantages of the loose-leaf binder include: (1) the fingers of the snap rings frequently become misaligned resulting in loss of or damage to the pages held in the loose-leaf binder, (2) loose-leaf binders are generally bulky since such binders have a ring mechanism, a spine panel, a front cover, and a back cover, and (3) the size of a standard loose-leaf binder is not adjustable to fit the thickness of the collection of pages being held in the loose-leaf binder.
Another device is a folding post binder, which has metal prongs that may be bent over and moveable slides or covers that hold the metal prongs in place. A disadvantage of the folding post binder is that the edges of the metal prongs sometimes are sharp, which is dangerous.
Abildgaard et al. U.S. Pat. Nos. Re 28,202, 4,369,013, and 4,620,724 disclose rigid plastic binding strips. Smooth studs formed on a first strip are inserted through perforated sheets and then through holes in a second strip. Then, pressure and/or heat is applied to the end of the studs to form a head which locks the strips and the sheets therebetween in assembled position. Abildgaard et al. binding strips require expensive mechanical equipment to create the heads on the studs, and these strips provide a permanent-type binding rather than an updatable-type binding.
Abildgaard et al. U.S. Pat. Nos. 4,674,906 and 4,685,700 disclose an updatable-type binding. Smooth studs formed on a first strip are inserted through perforated sheets and then through holes in a second strip. Then, the ends of the studs projecting from the holes in the second strip are bent over at a right angle into a groove to hold the first strip to the second strip. Binding thick books with such a binding is difficult because locking with the studs requires that the studs project far enough out of the holes in the second strip to permit bending of the studs.
Baumgart U.S. Pat. No. 950,768 and Giulie U.S. Pat. No. 3,970,331 also disclose binding strips. Studs formed on a first strip have teeth that engage a lip in a second strip to lock the first strip to the second strip. These ratchet-type devices require considerable and evenly distributed force to pass the studs of the first strip through the second strip, and once the devices are locked it is very difficult, if not impossible, to disengage the first strip from the second strip.